Some books are dangerous (but we still shouldn’t ban them)
Some books are dangerous, in the same way any media can be dangerous. Find a person whose mind is easily turned, and introduce them to some powerful and unwholesome rhetoric, add a sense of displacement from society and an obsession with proving themselves, and you can have a problem.
But, similar to the video games=violence ‘debate’ simply saying ‘this book is dangerous’ isn’t actually correct, and that’s why even the nastiest of books should be available for purchase. Obviously, some information should be kept away from the general public (like how to build a nuclear weapon) but in general we shouldn’t ban even the most distasteful of information.